Pirate DVDs that can hold more movies and TV shows than traditional DVD discs have become such a threat to China's video products market that the Shanghai General Team of Culture Inspection has kicked off a countrywide crackdown on illegal sales.

Last week, the city's team began a series of surprise raids on illegal DVD stores. Team officials refused, however, to disclose detailed plans for the effort.

"These highly compacted pirated discs will have a much greater negative impact on the audio-visual product industry than ordinary DVDs, so stopping their rampant development tops our working agenda," said a team official surnamed Chen.

Unlike traditional DVDs, which generally contain one movie or two to three episodes of a TV show, each highly compacted video disc, or HDVD, can hold up to 10 episodes of a TV series or several movies.

The disks, which first appeared in the city earlier this year, have become popular because they sell for about the same price as a regular pirate DVD - about 7 yuan (46p).

Among the most popular are discs containing TV shows made in South Korea and Japan, movies from Hong Kong and Taiwan as well as Hollywood blockbusters.

While the technology should make the picture quality of movies on HDVDs better than traditional DVDs, many are packed with too many movies and are drawing complaints from buyers.

"The scenes are always full of mosaics and sometimes the disc can't be played at all," said Vincent Chen, a local office worker. "But it's still more economical to get so many movies at such a low price."

Store owners said that HDVDs are always among the best sellers despite a high turnover rate caused by shoddy quality.

The bootleg market has grown so rapidly that the pirate discs are selling at about twice the rate of copyrighted discs, producers said.

"At this rate, pirate HDVD's impact on the country's audio-visual product market will be destructive," said Zhu Zhibing, a TV series producer told the Shanghai Morning Post.

Earlier this month, the Ministry of Culture also launched a nationwide campaign to combat the sale of pirate HDVDs. The crackdown will run through the end of next February, state officials said.